Due to the escalation of gasoline prices and the limitation of greenhouse gas emissions, it becomes a large issue to enhance the fuel efficiency of vehicles. One of measures therefor is weight reduction of vehicles, and weight reduction is also strongly demanded with respect to weather strip components. An approach adopted for the weight reduction of a rubber product such as weather strip component is to reduce the compounding amount of an additive such as reinforcing agent (e.g., carbon black, silica) that has a larger specific gravity than that of the rubber component and thereby decrease the specific gravity of the rubber product. Also, an approach by foaming a solid rubber portion of a weather strip has been adopted. Here, the blowing agent used is, for example, a chemical blowing agent such as azo compound, nitroso compound, sulfonyl hydrazide compound and azide compound, an inorganic blowing agent, or a thermally expandable capsule. As to the thermally expandable capsule, for example, those containing a low-boiling-point hydrocarbon in a shell wall are known (See Patent Document 1).
On the other hand, with respect to a vulcanizable rubber composition, a composition containing an ethylene/α-olefin/nonconjugated polyene copolymer rubber as the main material is known, and known examples thereof include a rubber composition obtained by finely dispersing an olefin-based resin in an ethylene-propylene-diene rubber (EPDM) (See Patent Documents 2 and 3).